With the rapid development of cities, more and more garbage and domestic sewage are generated. The garbage or domestic sewage includes harmful ingredients which will be danger to the atmosphere, water and earth, affecting ecological environment of cities and harming peoples health. Most cities in China have also been surrounded by garbage and domestic sewage. Therefore, garbage and domestic sewage treatment have become a major project in environmental protection. Currently, the garbage and domestic sewage are often treated separately.
Landfilling and incineration are two main garbage disposal methods. However, landfilling will occupy a large area, the site for landfilling is difficult to choose, and it is also difficult to recycle useful resources in the garbage in landfilling. Moreover, leachate and gas generated during the landfilling process are harmful to the surrounding environment. At the same time, the initial investment and operating costs of the landfilling become higher and higher with the advancing environmental standard. Wastes incineration can maximize waste reduction and decontamination. However, due to the expensiveness of its initial investment and operating costs, the secondary pollution of the burning exhaust, and the high requirement for the heat value and the moisture content of the raw materials, the method of the waste incineration may not be appropriate for treating organic garbage.
Fecal sewage treatment mainly uses the natural emission method that discharges the fecal sewage into rivers directly, or discharges the fecal sewage into water pipes after separating the precipitate by using the septic tank. Alternatively, an aerobic biological aeration process or an A2/O sewage treatment process can be used. However, area required for a sewage treatment plant is large; and it is difficult to solve the problem of air pollution and sludge emission. In addition, the waste recycling is improper, and actually has caused the waste of resources.
People have done a lot of research for solving above-mentioned problems such as environment pollution, inappropriate waste disposal, resource waste and etc.
Chinese patent publication number CN1314313A discloses a device for comprehensive treatment of fecal sewage and organic garbage. It separates feces and sewage from fecal sewage by a flotation process and by an overflow method in feces and water separating tanks correspondingly. The separated feces overflow into storage tanks. The organic waste is ducted into the storage tanks after crushed by s crusher. Then the feces and organic waste are fermented in the fermentation tanks to produce biogas. In this method, the separated and crushed feces need an anaerobic digestion process directly with a long reaction time and a low efficiency. Particularly, some substances that are difficult to digest in the anaerobic environment need a relatively longer digestive time. In addition, there are still some pollutants that are inappropriate to discharge directly after producing biogas.
Chinese patent publication number CN 101191116A discloses a combined-type fermentation pool, which is composed of retting pool equipped with heat exchangers and inside recirculation type biogas reactor. Straw, grass, processed fruit dregs and medicine dregs, and other solid form or sticky raw materials are retted directly in the retting pool. The acidification liquid from the fermentation, which is ducted into the biogas reactor through the grid of the bottom of the retting pool, is reacted to produce biogas by anaerobic fermentation. This combined-type fermentation pool with large area, long reaction time and external system contact is not suitable for the treatment of the daily sewage. The retting pool and the biogas reactor are always communicated with each other, which is not good for the occurrence of anaerobic digestion reaction, difficult to control, and produces gas with low efficiency in the biogas reactor. Additionally, as mentioned above, there are still some pollutants that are inappropriate to discharge directly after producing biogas.
Therefore, a more effective method and system are desired, which can treat domestic sewage and organic garbage efficiently and environmentally friendly, so as to achieve the goal of low pollution, or even nearly no pollution in waste discharging.